A variety of devices have been proposed or used for administering drugs transdermally. These devices are generally laminated composites that include a reservoir layer that contains the drug, a pressure-sensitive adhesive layer by which the device is attached to the skin, and a backing layer that forms the outer "skin" of the device. Depending upon the inherent permeability of the skin to a particular drug, the device may also include means for coadministering a percutaneous absorption enhancer or an element, such as a membrane interposed between the reservoir and the skin, that regulates the rate at which the drug and/or the enhancer is administered to the skin.
U.S. Pat. No. 4,379,454 and 4,460,372 described a device for coadministering a drug and a percutaneous absorption enhancer transdermally. The drug is presented to the skin at a rate in excess of that which the skin is inherently capable of absorbing and the enhancer is presented to the skin at a substantially constant rate that is sufficient to permit the skin to pass therapeutic levels of drug to circulation. The device includes a membrane interposed between a drug- and enhancer-containing reservoir layer and a pressure-sensitive adhesive layer that regulates the rate at which the enhancer is presented to the skin. In the commercial estradiol embodiment of this device (marketed under the mark ESTRADERM) the enhancer is ethanol and the estradiol-ethanol mixture is contained in the reservoir in a fluid form. Using such a form complicates the procedures for manufacturing the device and detracts from the ability to optimize certain physical characteristics of the device such as thickness, resiliency, and adhesiveness, that are associated with wearability.
Other patent publications relating to devices for administering estradiol transdermally are German Patent Publications 3,315,245 and 3,315,272, European Patent Publications 0013606 and 0040861 and U.S. Pat. No. 4,438,139.
Patent publications relating to transdermal delivery of opioids in general and fentanyl or fentanyl derivatives or analogs (sufentanil, carfentanil, lofentanil, and alfentanil) are EPA 0171742 and U.S. Pat. Nos. 4,588,580 and 4,626,539.
U.S. Pat. No. 4,435,180 described a transdermal drug-delivery device comprising a body of a mixture of elastomer and drug, the body being in a form such as an arm or wrist band which inherently creates a compressive force when worn to keep the body firmly in contact with the skin.
The focus of much of the prior art relating to transdermal drug delivery has been on the release kinetics of the drug or enhancer from the device. Because of this the design of most prior devices has centered about the achievement of desired drug release kinetics, and, for the most part has ignored or given only secondary consideration to mechanical properties than enhance its wearability and cosmetic acceptability. In this regard, the present invention provides a transdermal drug-delivery device that provides acceptable drug release kinetics as well as resiliency, thinness and, when permitted, breathability.